Indian Ocean FADs Causing Alarming Death Toll Of Silky Sharks

A new study has revealed alarming figures showing the huge amount of silky sharks that could be dying each year due to the use of FADs during tuna fishing in the Indian Ocean.

The enormous figure of 480,000-960,000 silky sharks dying annually in the Indian Ocean alone after entanglement within nets drifting with the assistance of fish aggregation devices (FADs) is the total estimated in a new research study undertaken by JD Filmalter and Laurent Dagorn. These two researchers have been working with the International Seafood Sustainability Foundation (ISSF) on the new report called #BycatchProject.

While not knowing the exact number of FADs being used in the Indian Ocean, the researchers monitored dozens of these floating manmade devices, in which the study outlined that as many as 35 percent of them during the research had snagged and killed at least one of these silky sharks. It is said that this ‘ghost’ fishing could amount to “5-10 times that of the known by-catch of this imperiled species for the region’s purse-seine fleet.” If silky sharks are not brought onboard along with the tuna catch, and remain entangled underwater under the FAD, they are not reported as by-catch, nor do they show up in tuna by-catch statistics on FADs.

The silky shark is one of the three most common oceanic sharks and can grow up to 3.3m in size, maturing at around 2m. Silky sharks reach earliest maturity at an age of 6 years. They are known to trail schools of tuna, its favored prey. While estimating the status of its stock is difficult due to the lack of nations reporting catch numbers of this shark species, it is thought that tuna fishing is resulting in juvenile silk sharks being overexploited, suggesting a potential long-term threat to its existence.

The Indian Ocean Tuna Commission (IOTC) issued a report in April, in which it expressed that silky shark stocks are under risk in Indian Ocean at current fishing effort level, and named it as one of the most vulnerable species in IOTC fisheries.

With tuna seiners using FADs to catch more than half of the word’s tuna, it leaves the study questioning the near-term viability of eliminating their use. However, the research did provide possible solutions to the long-term concern of this huge by-catch statistic that has been uncovered.

The study outlines that a simple alteration of the current FAD design to eliminate loose netting could virtually eradicate the shark mortality in the Indian Ocean, which some governments have already began to adopt, and will become a mandatory design change in the Indian Ocean over the next few years.